在chrome中输出调试信息
/* 在 chrome 的控制台输出信息 */
<script type="text/javascript">

   $( window ).scroll(function () {
    console.log($( window ).scrollTop());
    console.log($(document).height());
    console.log("bottom = ",$(document).height() - $( window ).scrollTop()-$(window).height() );
    console.log("sidebar bottom = " ,$(document).height()-$("#sideBar").offset().top-$("#sideBar").height());
   });
</script>